What makes those DNA markers turn dark?

Question

How do you get from taking a swab of cheek cells to making those dna markers go dark? Is there a "for dummies" version of the explanation?

Answer 1

You first lyse the cells, do a DNA extraction and then do PCR to amplify the DNA.

The product DNA is then run on a gel and stained with a dye.  The dye binds DNA and makes the desired amplified marker appear.

Or I have no idea what you're talking about.

Answer 2

Which DNA markers? From CSI? A home kit?

Answer 3

First you add a enzyme (like using scissors) to your sample. It cuts the DNA up into different sized pieces. The DNA pieces are then dyed with a dye so that they appear in the jell- simple as that.

As you run the electric current through the jell, it separates the pieces according to length.

Answer 4

Ok this is a tough question to answer breifly but I will try.  The "dark"ness you are refering to is a DNA "fingerprint"  It looks like a UPC bar code like on things you buy at the groceries store.  The pattern that you see in these dark bands is different for everybody except for identical twins (because they have identical DNA right?).  So what makes them go dark?  The DNA fingerprints are actually x-ray films.  When you get your foot x-rayed they shoot a beam of x-rays through your foot and onto x-ray film.  The x-rays make the film turn black except where the bones stop them.  The more dense the bone or skin or cartilage, the lighter they show up on the film.  X-ray film is used to make DNA fingerprints but its kind of backwards.  Scientist make a "DNA probe" that will stick to a known region of human DNA.  This probe is made with radioactive atoms.  Then they let this radioactive probe find and stick to the know region of DNA (the DNA markers).  Once this is done, any extra radioactive probe is washed away so only the known areas of the DNA are radioactive.  Then x-ray film is place on top of the DNA and only the DNA markers will make the film turn black.  Now this is only an answer to the "dark" question.  How these patterns are formed and are different between people is another tough question.  How looking at these can tell you who you are related to is another.  I hope this is the answer you are looking for.